Atrial cardiomyopathy has been defined as any electrical and/or mechanical dysfunction of the left atrium. This dysfunction can lead to Atrial Fibrillation (AF), which is responsible for a third of all ischemic strokes. However, atrial fibrillation is not the only left atrium-related cause of stroke. Indeed, changes in LA wall mechanics, caused by remodelling of the wall (fibrotic myocardium mostly), can result in thrombogenic blood flow patterns. Structural and electrical changes in the LA are interconnected and their effect on atrial flow patterns are not fully understood. This project aims to develop new clinical diagnosis tools to detect the biomechanical changes in the LA wall and the alterations of the intra-atrial flows to anticipate the risks of strokes. For this, this project with combine characterisation methods from both structural and fluid points of view. This multidisciplinary project will answer to the following four objectives: - To develop a metric to quantify locally the degree of left atrium wall fibrosis in terms of mechanics and to understand its effect on the wall mechanical behaviour, based on the mechanical and biological characterisation of surgical biopsies, - To develop a methodology to measure left atrium mechanical properties in vivo for patients, from CRM images - To create a mechanistic link between left atrium flow patterns and the risk of thrombus formation, based on the analysis of 4D MRI data, - To assess how much fibrosis impacts the risk of thrombus formation in the left atrium. This project could lead to the development of new tools for the diagnostic of atrial cardiomyopathies, which would help the development of new treatment strategies.

The PRME LINEN project brings together five researchers from the Mechanics & Direct Manufacturing Processes team of the LGF laboratory, CNRS UMR 5307, for a total of 1.7 FTRE. This project aims for a better understanding of the manufacturing of flax fibre-based composites through resin infusion processes, taking into account the intrinsic variability of natural fibres and the resulting local phenomena. Three tasks are proposed, corresponding to 2 PhD theses and an 18-month post-doc. Task 1 involves the complete characterisation of infusion mechanisms occurring during manufacturing, at both intra- and inter-yarn scales within the same experiment. This dual-scale characterisation of flow using full-field optical methods will provide valuable information on the fluid-fibre interactions that control the impregnation of the fibre network. This information will be processed in conjunction with Task 2, which aims to characterise these same mechanisms using 2D finite element simulations on representative volumes derived from µ-CT, in order to extract effective properties through a scale transition procedure. The dependency of these homogenised properties (permeability, saturation, capillary pressure) on the intrinsic geometric variability of fibres or yarns (depending on the scale considered) will be quantified using Gaussian processes. Finally, Task 3 will complement this description by developing 3D simulations of resin infusion at the inter-yarn scale. This involves simulating resin flow in simplified meso-structures or structures derived from µ-CT images. This approach will capture phenomena induced by geometric variations along the yarns (variation in fibre volume fraction) and analyse them in relation to measurements made in Task 1.